Lumbar disc herniation

1

Describe the prevalence and natural history of lumbar disc herniation. contrast the prevalence and natural history of lumbar disc herniation and low back pain.

The lifetime prevalence of a symptomatic lumbar disc herniation in the adult population is approximately 2%. The natural history of sciatica secondary to lumbar disc herniation is spontaneous improvement in the majority of cases. Among patients with radiculopathy secondary to lumbar disc herniation, approximately 10%–25% (0.5% of the population) experience persistent symptoms. These statistics are in sharp contrast to low back pain , which has a lifetime prevalence of 60%–80% in the adult population. Although the natural history of acute low back pain is favorable in many patients, recurrent pain is common, and successful management of patients with chronic symptoms remains an enigma.

2

What is the typical history of a patient with a lumbar disc herniation?

Often there is an attempt to link the onset of back and leg pain with a traumatic event, but many patients will report experiencing intermittent episodes of back and leg pain for months or years. Factors that tend to exacerbate symptoms include physical exertion, repetitive bending, torsion, and heavy lifting. Pain most commonly originates in the lumbar area and radiates to the sacroiliac and buttock regions. Radicular pain typically becomes dominant and extends below the knee in the distribution of the involved nerve root. Radicular pain may be accompanied by paresthesia, weakness, and/or reflex changes in the distribution of the involved nerve root. Patients with a disc herniation commonly report that pain in the leg is worse than low back pain, although patients may occasionally present with substantial low back pain. Pain tends to be exacerbated by sitting, straining, sneezing, and coughing, and relieved with standing or bed rest.

3

Define cauda equina syndrome.

Cauda equina syndrome is defined as a complex of low back pain, sciatica, saddle hypoesthesia, and lower extremity motor weakness in association with bowel or bladder dysfunction. The mode of onset may be slow or rapidly progressive. The most common cause of cauda equina syndrome is a central lumbar disc herniation at the L4–L5 level. Prompt surgical treatment is advised.

4

Outline key points in the physical examination of a patient with a suspected lumbar disc herniation.

The patient should be undressed. Observation may reveal the presence of a limp or a list (sciatic scoliosis). Spinal range of motion is assessed. A complete neurologic examination (sensory, motor, reflex testing) is performed to identify the involved nerve root. Nerve root tension signs are evaluated. Hip and knee range of motion are assessed to rule out pathology involving these joints. Peripheral pulses (dorsalis pedis and posterior tibial) are assessed to rule out peripheral vascular problems. A rectal examination is performed in patients suspected of having cauda equina syndrome.

5

What are nerve root tension signs?

Tension signs are maneuvers that stretch the sciatic or femoral nerve and in doing so further compress an inflamed nerve root against a lumbar disc herniation. Both the symptomatic and contralateral lower extremities should be examined. The supine straight leg raise test (Lasègue test) and its variants (sitting straight leg raise test, bowstring test) increase tension along the sciatic nerve in the symptomatic lower extremity and are used to assess the L5 and S1 nerve roots. A positive supine straight leg test reproduces symptoms between 30° and 70° of hip flexion. Tests involving the symptomatic lower extremity are sensitive but not specific for diagnosis of sciatica. The contralateral straight leg raise test (crossed straight leg test) reproduces pain in the symptomatic leg by raising the unaffected leg, and is a highly specific test for diagnosis of lumbar disc herniation. The femoral nerve stretch test (reverse straight leg raise test) increases tension along the femoral nerve and is used to assess the L2, L3, and L4 nerve roots.

6

Compare and contrast sciatica with other common clinical syndromes presenting with low back and/or lower extremity pain symptoms.

• Sciatica: Leg pain rather than low back pain is typically the predominant symptom, although some patients may also present with substantial low back pain. Neurologic symptoms and signs are found in a specific nerve root distribution. Nerve root tension signs are present.

• Nonmechanical back and/or leg pain: Pain is constant and minimally affected by activity and unrelieved with rest. Pain is usually worse at night or early morning (e.g., spinal tumor, infection).

• Mechanical back and/or leg pain: Pain is exacerbated by activity, changes in position, or prolonged sitting. Pain is relieved with rest, especially in the supine position (e.g., degenerative disc pathology, spondylolisthesis).

• Neurogenic claudication: Low back and buttock pain, radiating leg or calf pain, worse with ambulation, worse with spinal extension, and relieved with flexion maneuvers, with absent nerve root tension signs (e.g., spinal stenosis).

7

When clinical examination suggests the presence of an acute lumbar disc herniation, what is the preferred imaging test to confirm the diagnosis?

Magnetic resonance imaging (MRI) is the preferred imaging test because it provides the greatest amount of information about the lumbar region. It is unparalleled in its ability to visualize pathologic processes involving the disc, thecal sac, epidural space, neural elements, paraspinal soft tissue, and bone marrow. However, caution is indicated when interpreting results of MRI scans due to the high frequency of disc abnormalities in asymptomatic patients. It is critical to correlate imaging findings with clinical examination. Although lumbar radiographs cannot show a lumbar disc herniation, standing radiographs are advised prior to referral for MRI in order to define regional lumbar anatomy and diagnose other potential pathologies such as spondylolisthesis.